Control means for pressure relief in hydraulic machines



United States Patent [72] Inventor Gaston Sebastien Forichon l7] ruedeBillancourt, Boulogne sur Seine, France [21] Appl. No. 704,379

[22] Filed Feb. 9, 1968 [451 Patented Oct. 20, 1970 [32] Priority Feb.17,1967, [33] France, [31 1 95,456

[54] CONTROL MEANS FOR PRESSURE RELIEF IN 2,827,765 3/1958 Towler i.IOU/52X FOREIGN PATENTS 565,259 11/1944 Great Britain 100/52 PrimaryExaminerBilly J. Wilhite Attorney-Wolf. Greenfield and Sacks ABSTRACT: Acontrol means for relieving pressure of the working fluid in a hydraulicoperated machine having a press piston mounted for reciprocal movementin a hydraulic chamber with the chamber defining a piston workingchamber portion and a piston return portion with a reservoir for aworking fluid. The control means comprises a decompression valve bodymounted in a valve chamber with one side of the body extending on oneside of the valve seat and a second part of the body extending on asecond side of the valve seat. Fluid communication means connect thevalve chamber with the pressure chamber portion. A means for moving thebody from the seat to cause the working fluid to initiate further'movement of the valve body is provided. A switch means is operativelyassociated with the valve body with for returning fluid from thepressure chamber portion to the reservoir on the further movement of thevalve body whereby progressive pressure relieving of the working fluidin the pressurechamber portion is carried out and brutal shocks whichmight damage material are avoided.

Patented Oct. 20, 1970 Sheet Patented Oct. 20, 1970 3,534,679

Sheet 4' of4 WVEA/TOE CONTROL MEANS FOR PRESSURE RELIEF IN HYDRAULICMACHINES SUMMARY OF THE INVENTION The invention concerns a device forthe control of the decompression of the working fluid in hydraulicmachines such as presses, characterised in that it comprises adecompression valve mounted on a damper, the valve being immersed in achamber in communication with the pressure chamber of the press piston,which valve is lifted from its seat by the working piston as soon as thelatter has effected its shaping operation, this liberating thecompressed fluid which takes over the valve and urges it downwardlyuntil it comes to act through the intermediary of a switch member, on acontact providing inversion of the control electrovalves, the compressedfluid then being returned to the reservoir, this permitting aprogressive decompression of the working fluid and thus avoiding thebrutal shocks which can have a harmful effect on the longevity of thematerial.

According to a feature of the invention the valve is mounted on ahydraulic damper and has on the one hand a conical portion coming intocontact with its seat, and on the other hand a consequent annularshoulder, such that the compressed fluid which escapes from the pressurechamber of the press piston when the valve is lifted from its seatencounters a surface which is sufficiently large to be able to entrainthe decompression valve in the downward direction so that this valveactuates through the intermediary of a cap integral therewith, a switchgear stopping the arrival of fluid under pressure in the pressurechamber of the press piston.

According to another feature of the invention, the press piston isprovided with a table which is sliding with respect to a control rodupon which is mounted a nut which can be adjusted for position, the rodbeing provided at one of its ends with a cylindrical head which actsagainst the cap integral with the stem of the decompression valve, insuch a way that when the press piston has descended to its lowest presetpoint, its table which slides with respect to the rod, comes intocontact with the adjustable nut of which the position has beenpredetermined, which has the effect of exerting a traction force on therod and consequently on the decompression valve which is thus liftedfrom its seat to be taken over by the working fluid hitherto compressedin the pressure chamber of the press piston.

The invention also concerns hydraulic machines such as presses, equippedwith a control device according to one or other of the variousembodiments or the like.

BRIEF DESCRIPTION OF THE DRAWINGS A device according to the invention isillustrated by way of nonlimitative example in the attached drawings, inwhich:

FIG. 1 is a plan view showing the device according to the inventionadapted to a hydraulic press, the installation being ready foroperation, i.e. the press piston is in its raised position and theoperator has not yet pressed the control button of the motor.

FIG. 2 is a plan view similar to FIG. 1 illustrating the device in thecourse of operation in the form of rods.

FIG. 3 is a plan view similar to FIG. 1 the hydraulic group not beingshown, the device operating not by rods but by manometric action.

FIG. 4 is a detail view showing the safety device in action.

The essential aim of the invention is in some manner to provide acontrol device for the relief of pressure on or decompression of thefluid after the press piston has effected its pressing operation.

The invention also lies in providing a control device which permits aprogressive decompression of the working fluid in order to avoid anybrutal shock which can cause premature deterioration of the material.

Finally the device according to the invention also sets out to providewith precision, particularly on a hydraulic press, the control in thethickness or pressure of the parts subjected to deformation and topermit on the other hand the precise arresting of the workingoperations; in other words to permit a rapid cycle while retaining aprecise and regular cycle.

To carry this out, and according to the invention, the device is madeaccording to an embodiment so as to be able to act either by a system ofrods if operation is effected as a function of a determined height ofthe part to be shaped, or by manometric action if operation is effectedstarting from a given pressure.

BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS The following descriptionwill successively take up the two possibilities grouped in the samedevice and operating by means of one and the same decompression valve.

A. ROD SYSTEM OPERATION According to the embodiment shown in FIG. 1, thedevice applied to a hydraulic press comprises a decompression valve Imounted vertically movable in a chamber 2 which is in conimunicationthrough a conduit 3 with a pressure chamber 4 located behind theshouldered press piston 5.

This decompression valve has different diameters and par ticularly has ahead 1,, ofwhich the diameter D is greater than the small diameter dlocated at the precise point at which the conical surface 1 of the valvecomes into contact with its annular seat S projecting in the interior ofthe chamber 2.

The decompression valve comprises moreover an annular shoulder 1 ofwhich the diameter determines a large surface D this shoulder being asealing sliding fit in the interior of the chamber 2.

The decompression valve is mounted on a hydraulic damper 7 so that itspossible downward displacement is controlled by a restriction 8connecting the chamber of the hydraulic damper to the reservoir 9.

A return spring 10 acting on the bottom face of the decompressionchamber tends constantly to urge this valve in an upward direction.

The stem 1., of the decompression valve I is terminated at its lowerpart by a cap 11 showing the particular feature of having a projectingcam 11,, the cap receiving moreover the head 12 of a rod 12 upon whichis screwed a nut 13 ofwhich the position is adjustable.

The press piston 5 is provided with a table 6 adapted to be displacedduring the shaping operation with respect to the rod 12 so as to comeinto abutment against the nut 13 of which the position has been preset,as will be explained hereinafter.

The hydraulic group substantially comprises a motor M and a pump P incommunication with the reservoir 9 through a conduit 14, this pump alsobeing in communication with an electrovalve 15 through the conduit 16,passing through a safety valve 17, and finally with the pressure chamber4 of the press piston through the conduit 18, an electrovalve 19permitting the inversion of the fluid pressures on the two faces of thepress piston 5.

In FIG. 1, the safety valve 17 is connected to the reservoir 9, i.e. thefluid from the pump may pass to this reservoir while maintaining asufficient pressure which is a function of the pressure determined bythe calibration of the clack valve 20 to permit the upward return andthe maintenance in the raised position, of the working piston 5, whilethe electrovalve 19 is in this case connected in parallel so that thefluid contained in the pressure chamber 4 can flow freely through theconduit 21 into the reservoir 9 while the fluid under slight pressure isdirected toward the chamber 4 of the working piston through the conduitsl8 and 22.

In the rod system operation, it is necessary to neutralise themanometric action by immobilising the pilot valve 23 by the action of aspring 24 having a pressure greater than that which will be attained atthe culminating working point in the pressure chamber 4 of the workingpiston.

In this state, the press piston is therefore in the raised position; thetable 6 of this piston is removed from the nut 13 OPERATION (FIG. 2)

When the operator presses the general control button, he sets in motionthe motor M and causes inversion of the two electrovalves and 19.

Thus the safety valve 17 is disconnected from the conduit 16. The fluidunder pressure delivered by the pump P is sent into the working chamber4 through the conduits 18 and 21 by means of the electrovalve 19 whichconnects these conduits, a nonrcturn clack valve 25 preventing the fluidfrom returning toward the pump.

Moreover the pressure which hitherto prevailed in the chamber 4, of thepress piston, decreases from the fact that the chamber is directlyconnected to the reservoir 9 through the conduits 22 and 26.

Thus the pressure of the fluid increases in the pressure chamber 4 anddecreases inversely in the chamber 4,. When the pressure of the workingfluid has attained a sufficient value to overcome the inertia of theworking piston 5, the working piston 5 is then urged downwardly in thedirection indicated by the arrow H and comes into contact with the partto be shaped 27.

The travel of the working piston 5 is then interrupted at a giventhickness of the part 27 by the press table 6 coming into contact withthe nut 13, of which the position has been preset so that when the table6 encounters the nut 13, the part 27 has been deformed to a preciseheight calculated in advance.

' As soon as the pressing table 6 comes into contact with the preset nut13, this table draws the rod 12 in a downward direction, whichconsequently entrains the decompression valve 1 with which it is inconnection through the assembly cap 11.

This travel of the compression valve is greatly reduced by the factthat, as soon as the valve is lifted from its annular seat S, the highlycompressed fluid escapes into the annular passage defined between theseat S and the valve stem 1 this fluid thus coming into contact with thecylindrical shoulder 1,, of which the pressure surface D, is greaterthan that determined by the diameter D of the head 1, of the valve.

Thus the compressed fluid entrains in a downward direction thedecompression valve which moves rapidly until it blocks the aperture 45,and then moves slowly, in view of the presence of the hydraulic damper 7and the restriction 8.

The fluid coming into contact with the pressure surface 1,, then escapesthrough the channel 28 to return to the reservoir 9.

At the same time the cap 11 comes into contact with the switch gear 29which inverses the electrovalves 15 and 19 so as to return theseelectrovalves to the position which they occupy in FIG. 1.

As soon as the electrovalves l5 and 19 are inverted, the pump P isbrought back into communication through the conduits l6 and 30 with thereservoir 9, although the fluid maintains a sufficient pressure to movethe piston 5 upwardly, this pressure being determined by the clack valve20.

As soon as the pressure has sufficiently decreased in the chamber 4 ofthe working piston, and consequently in the chamber 2 of thedecompression valve, the spring 10 returns the decompression valve so asto again apply it against its annular seat S, the valve thus remainingin position whatever may be the pressure which will prevail in thechamber 2, due to the fact that the valve head 1, has a working surfaceD which is greater than the diameter d taken in the vicinity of the seatof this valve.

B. MANOMETRIC ACTION When the control device according to the inventionoperates by manometric action, it is necessary to neutralise the controlby rods. In order to provide this neutralising action, it is sufficientto move away the adjusting nut 13, so that the pressing table 6 can nolonger come into contact with this nut, even when the press piston is inits lowest position.

Operation by manometric action is essentially provided by a pilot valve23 of which the terminal face 23, is immersed in the chamber 2 in whichis housed the decompression valve.

This pilot valve is strongly applied on to its seat 31 by the calibratedspring 24 of which one of the ends rests in a cap 32 which is applied tothe rear face 23 of the pilot valve, the spring 24 being calibrated at apredetermined force by an adjusting nut 33 which is displaced in frontof a vernier 34: this vernier 34 permits very precise calculation of thepressure which must be applied to the spring 24 so that this spring 24applies to the pilot valve 23 a force equal to that which the workingfluid will apply to the terminal face 23, of the pilot valve 23 when thepressure has achieved the desired value in the chamber 4 andconsequently in the chamber 2.

OPERATION At the beginning, the hydraulic installation (not shown inFIG. 3), is arranged in the same manner as that illustrated in FIG. 1,Le. the safety valve 17 is in communication with the reservoir 9 whileconserving a sufficient pressure to maintain the press piston in theraised position, this pressure being provided by the calibrated clackvalve 20. On the other hand the electrovalve 19 is positioned as in FIG.1, i.e. the conduit 18 of the pump P is not in communication with theconduit 21 leading to the pressure chamber 4.

As soon as the operator presses the control button, this buttondetermines the inversion of the two electrovalves l5 and 19 so as toclose the safety valve 17 and to bring into communication the conduit 18with the conduit 21 so that the compressed fluid delivered by the pump Pis delivered to the pressure chamber 4 so as to exert a high degree ofpressure on the rear face of this piston to urge it downwardly.

When the pressure of the working fluid contained in the pressure chamber4 has attained a value slightly greater than that exerted on the pilotsurface 23 by the calibrated spring 24, the pilot valve is then liftedfrom its seat by the action of the fluid on its terminal surface 23,,which causes the fluid to rush into the chamber 35 and then coming toact on the face D, of the annular shoulder 1 of the decompression valve1, passing through the delivery tube 36.

As soon as the fluid lifts the decompression valve 1 very slightly fromits seat S, the compressed fluid contained in the chamber 2 then rushesdirectly through the annular channel defined between the seat S and thevalve stem 1,, to come to act against the surface D, and thus entrainingthe decompression valve downwardly, the displacement of which valve iscontrolled by the damper 7, the return spring 10 and the restriction 8of the conduit leading to the reservoir 9.

Here too as in the case of control by rod system, the cap 11 integralwith the valve stem 1, comes into contact with its cam 11, with theswitch gear 29 which again inverses the electrovalves l5 and 19.

C. SAFETY The safety of the device, permitting the instantaneous arrestof the machine in case of difficulties or disturbances particularly dueto poor presentation of the parts, is assured by an electrovalve 37,shown in FIGS. 1 to 4, this electrovalve being connected when thehydraulic press is operating normally, through a conduit 38 to thechamber 39 located behind the head 1, of the decompression valve 1,which conduit is itself in communication through the electrovalve 37with the conduit 40 leading to the reservoir 9; in this state, thepressure is practically nil in the chamber 39.

ln case of difflculty, it is sufficient for the operator to press thepress button 41 to bring this press button into contact with thecontacts 42 which actuate the electrovalve 37 in such a manner as todisplace it in the direction indicated by the arrow G (FIGS. 4, S), inorder to bring the conduit 38 into communication with the conduit 43which is itself connected to the pressure chamber 4 in which the workingfluid is compressed.

As soon as this communication is established, the working fluid isimmediately passed into the chamber 39 through the conduits 38 and 43,which immediately entrains the compression valve downwardly, lifting itfrom its seat 5, whereupon the pressure fluid immediately rushes intothe annular space defined between the stem 1 of the valve and theannular seat 5 to come to act on the surface 1 and thereby cause the entrainment of the decompression valve, the displacement of which iscontrolled by the hydraulic damper 7, the return spring and therestriction 8 of the conduit 44 leading to the reservoir 9.

Here too as in the case of operation by rod system or in the case ofmanometric action, the cap 11 comes into contact with the switch gear 29which inverses the electrovalves 15 and 19 which immediately returns theworking piston to its raised position, the pressure decreasing in thechamber 4 and on the contrary increasing in the chamber 4,.

Obviously this device can be applied to any hydraulic machine whatever,such as a hydraulic press, ram or the like, Le. in all cases in which itis necessary progressively to decompress a fluid subjected to a highpressure, in a manner such as to prevent a too brutal decompressionwhich entails the risk of causing deterioration of the material.

It is obvious that the invention is not limited to the embodimentshereinbefore described and illustrated, and it is possible according tochoice, either to construct the device with the rod system control only,or to construct it with the manometric action control only, or againwith both types of control, as illustrated in FIGS. 1 to 3.

lclaim:

1. In a hydraulic operated machine having a press piston mounted forreciprocal movement in a hydraulic chamber, said hydraulic chamberdefining a piston working pressure chamber portion and a piston returnportion, with a reservoir for a working fluid, the improvementcomprising:

a control means for relieving pressure of said working fluid in saidpressure chamber portion after said piston has moved in a firstdirection;

said control means comprising a decompression valve body;

a valve chamber for said valve body defining a seat for said body with afirst portion of said body extending on one side of said seat and asecond portion of said valve body extending on a second side of saidseat;

fluid communication means connecting said valve chamber with saidpressure chamber portion;

second fluid communication means connecting said valve chamber with saidreservoir;

means for moving said body from said seat to cause said working fluid tocause further movement of said valve body; and

switch means operatively associated with said valve body for returningfluid from said pressure chamber portion to said reservoir on saidfurther movement of said valve body whereby progressive pressurerelieving of said working fluid in said pressure chamber portion can becarried out and brutal shocks avoided.

2. The improvement of claim I wherein said valve body is mounted on ahydraulic damper.

3. The improvement of claim 2 wherein a return spring constantly urgessaid control valve body against said seat with a predetermined force.

4. The improvement of claim 2 wherein said means for moving said bodyfrom said seat is interconnected with said piston and actuated by saidpiston,

said second portion of said valve body carrying an annular shoulderdefinin a surface having a larger area than a facing surface on saidirst portion of said piston whereby when sax valve is moved from saidseat, said working fluid escapes from said pressure chamber portion andentrains said valve body to cause actuation of said switch means.

5. The improvement of claim 4 wherein said means for moving said bodyfrom said seat comprises a control rod having an adjustable stop meansthereon,

said control rod being interconnected with an extension of said valvebody,

a table interconnected with said piston for movement therewith,

said adjustable stop means being adjusted to engage said table uponpredetermined movement of said piston to cause said valve body to bemoved from said seat.

6. The improvement of claim 5 wherein said extension of said valve bodyis substantially coaxial therewith and carries a downwardly opening cupmeans within which said rod is axially slidable,

said rod and said piston being substantially parallel.

7. The improvement of claim 4 wherein said means for mov ing said bodyfrom said seat comprises a pilot valve actuated by manometric action,said pilot valve having a valve body in fluid contact with said valvechamber whereby pressure in said valve chamber is communicated to saidpilot valve body.

8. The improvement of claim 7 wherein said pilot valve body isinterconnected with a calibrated spring having a predetermined degree ofcompression,

adjusting screw means for compressing said calibrated spring inassociation with a calibrated scale to preset the fluid pressurerequired to move said pilot valve body,

second fluid communication means interconnecting said pilot valve andsaid second portion of said control valve body whereby, when saidworking fluid in said control valve chamber reaches a predeterminedpressure, said pilot valve body is moved to connect said second fluidcommunication means with said control valve chamber allowing workingfluid to act on said second portion of said valve body and entrain it tomove said control valve body from said seat and cause further movementwhich actuates said switch means.

9. The improvement of claim 4 and further comprising a second controlvalve chamber positioned on a side of said first control valve bodyportion,

and electropressure valve for controlling fluid pressure in said secondcontrol valve chamber whereby action of said electropressure valve movessaid control valve body from said seat whereupon said working fluidentrains said control valve body to progressively move it and therebyrelieve pressure in said pressure chamber portion.

